Investigating Neuromodulation and Hemodynamics of the Muscle-Brain Axis in Patients with Sarcopenia Using Near-Infrared Spectroscopy
Sarcopenia is often accompanied by chronic diseases and conditions such as osteoporosis, obesity, and cognitive impairment, posing a serious threat to the quality of life of approximately 10% of older adults worldwide. Recent studies have also found that sarcopenia is closely associated with brain degeneration, including dementia and declines in verbal fluency and cognitive function. Although the mechanisms linking sarcopenia and cognitive impairment remain insufficiently studied, substantial evidence suggests that crosstalk between muscle and the brain plays an important role. Building on our previous research into the muscle-brain axis, we have developed methods for measuring cerebral and muscular hemodynamics in both healthy and disease models, including stroke, as well as neuromodulation mechanisms for intervention. This study aims to investigate the plasticity of muscle-brain crosstalk through near-infrared spectroscopy (NIRS) and myokine biomarkers within the framework of the muscle-brain axis. In addition, a neuromodulation protocol may be designed to address potential cognitive impairment associated with sarcopenia.
To investigate hemodynamic crosstalk between muscle and the brain, a dual-wavelength continuous-wave NIRS system will be developed in the first year to measure non-invasive cerebral blood flow (CBF) and changes in muscular hemodynamics. During handgrip strength assessments, the phase and amplitude coherence between biceps and prefrontal hemodynamics can be monitored using the temporal correlations measured by CW-NIRS and NIRx.
In the second year, muscle-brain crosstalk and myokine biomarker measurements will be compared among healthy participants and participants with early-stage or severe sarcopenia. Using a neuromodulation prototype based on the high-density (HD) brain stimulation device developed in our previous research, a proof of concept for effectively modulating brain activity and muscular hemodynamics in participants with sarcopenia will be evaluated in a clinical setting. In the third year, the PLL-based wireless NIRS system, which has a sampling rate of up to 50 Hz compared with approximately 10 Hz for commercial NIRx systems, will be extended to capture fast optical signals at a higher sampling rate of more than 200 Hz. These signals can provide a high degree of correlation with neuromodulation signals.
Monitoring muscle-brain crosstalk and myokines is expected to provide indicators for examining the relationships among skeletal muscle loss, degenerative diseases, and aging-related risks. In addition to conventional exercise training and nutritional supplementation, this study will develop a potential treatment strategy using an innovative muscle-brain neuromodulation protocol, opening new avenues for slowing or reversing the progression of sarcopenia. The ultimate goal is to enable wireless high-definition theta-burst stimulation (HD-TBS) in home care settings for the daily management of sarcopenia and potential cognitive impairment.
Research highlights:
- Development of a wearable functional near-infrared spectroscopy system
- Interpretability and clinical validation
- Muscle-brain crosstalk and hemodynamics